Received: 26 Jan 2022 – Discussion started: 04 Feb 2022
Abstract. The characteristics of the CISE-LOCEAN sea water isotope data set (δ18O, δ2H, later designed as δD) are presented. This data set covers the time period from 1998 to 2021 and currently includes close to 8000 data entries, all with δ18O, three quarters of them also with δD, associated with a time and space stamp and usually a salinity measurement. Until 2010, samples were analysed by isotopic ratio mass spectrometry, and since then mostly by cavity ring-down spectroscopy (CRDS). Instrumental uncertainty on individual data in this dataset is usually with a standard deviation as low as 0.03 / 0.15 ‰ for δ18O and δD. An additional uncertainty is related to uncertain isotopic composition of the in-house standards that are used to convert daily data into the VSMOW scale. Different comparisons suggest that since 2010 the latter have remained within at most 0.03 / 0.20 ‰ for δ18O and δD. Therefore, combining the two suggests a standard deviation of at most 0.05 / 0.25 ‰ for δ18O / δD.
Finally, for some samples, we find that there has been evaporation during collection and storage, requiring adjustment of the isotopic data produced by CRDS, based on d-excess. This adds an uncertainty on the adjusted data of roughly 0.05 / 0.10 ‰ on δ18O and δD. This issue of conservation of samples is certainly a strong source of quality loss for parts of the database, and ‘small’ effects may have remained undetected.
The internal consistency of the database can be tested for subsets of the dataset, when time series can be obtained (such as in the southern Indian Ocean or North Atlantic subpolar gyre). These comparisons suggest that the overall uncertainty of the spatially (for a cruise) or temporally (over a year) averaged data is on the order of or less than 0.03 / 0.15 ‰ for δ18O / δD. On the other hand, 17 comparisons with duplicate sea water data analysed in other laboratories or with other data sets in deep regions suggest a larger scatter. When averaging the 17 comparisons done for δ18O, we find a difference close to the adjustment applied at LOCEAN to convert salty water data from the activity to the concentration scale. Such a difference is expected, but the scatter found suggests that care is needed when merging datasets from different laboratories. Examples of time series in the surface North Atlantic subpolar gyre illustrate the temporal changes in water isotope composition that can be detected with a carefully validated dataset.
Reviews for “The CISE-LOCEAN sea water isotopic database (1998-2021)”
Authored by Reverdin et al.
Submitted to Earth System Science Data
Summary and overall opinion:
This study compiles and discusses the uncertainty assessment of seawater del-18O and del-2H. The data set will be very useful for many applications such as constraining ocean circulation. The main issue is with writing and figure captioning and labelling, some of which I have listed below. Overall, I recommend this manuscript for publication after authors edit it thoroughly for grammar and phrasing.
Minor comments:
Abstract:
Line 8: It’d be better to change “0.03 / 0.15‰ for δ18O and δD.” to “0.03 and 0.15‰ for δ18O and δD, respectively.” You can apply this comment to any setup like this in the entire manuscript.
Introduction:
Line 33: change “designed as” to “termed as”.
Line 53: you can use one “in” and name all the basins.
Line 58: do you mean “some samples were also run”?
Line 72: add the “to which” after “extent”.
Uncertainties:
Line 132-133: change “before been analyzed” to “before analysis”.
Line 139: change “was” to “were”.
Line 150: change “this way … ” to “this technique is applied to minimize the inter-sample contamination …”.
Line 182: change “sea water” to “seawater”.
Line 219: change “As commented above” to “As mentioned above”.
Figure 1: Please add panel labels (a, b, c, and d) and axis labels to the figure.
Figure 3: add labels to each panel. Also you do not need to say “six maps”. Readers can see the number of maps. Just label them and caption each label separately. Also add axis label to the color bars.
Reviews for “The CISE-LOCEAN sea water isotopic database (1998-2021)”
Authored by Reverdin et al.
Submitted to Earth System Science Data
Summary and overall opinion:
This study compiles and discusses the uncertainty assessment of seawater del-18O and del-2H. The data set will be very useful for many applications such as constraining ocean circulation. The main issue is with writing and figure captioning and labelling, some of which I have listed below. Overall, I recommend this manuscript for publication after authors edit it thoroughly for grammar and phrasing.
Minor comments:
Abstract:
Line 8: It’d be better to change “0.03 / 0.15‰ for δ18O and δD.” to “0.03 and 0.15‰ for δ18O and δD, respectively.” You can apply this comment to any setup like this in the entire manuscript.
Introduction:
Line 33: change “designed as” to “termed as”.
Line 53: you can use one “in” and name all the basins.
Line 58: do you mean “some samples were also run”?
Line 72: add the “to which” after “extent”.
Uncertainties:
Line 132-133: change “before been analyzed” to “before analysis”.
Line 139: change “was” to “were”.
Line 150: change “this way … ” to “this technique is applied to minimize the inter-sample contamination …”.
Line 182: change “sea water” to “seawater”.
Line 219: change “As commented above” to “As mentioned above”.
Figure 1: Please add panel labels (a, b, c, and d) and axis labels to the figure.
Figure 3: add labels to each panel. Also you do not need to say “six maps”. Readers can see the number of maps. Just label them and caption each label separately. Also add axis label to the color bars.
The CISE-LOCEAN sea water stable isotope data set has close to 8000 data entries. The δ18O and δD isotopic data measured at LOCEAN have uncertainties of at most 0.05 / 0.25 ‰. Some data were adjusted to correct for evaporation. The internal consistency is explored indicating that the data can be used to investigate time and space variability to within 0.03 / 0.15 in δ18O / δD . 17 comparisons with data analyzed in other institutions suggests larger differences with other data sets.
The CISE-LOCEAN sea water stable isotope data set has close to 8000 data entries. The δ18O and...
